Instinct

Abstract

Instinct is a type of motivation in the MeSH classification: stereotyped patterns of response, characteristic of a given species, that have been phylogenetically adapted to a specific type of situation. This article covers the ethological account of releasers, key stimuli and fixed action patterns, the critiques that challenged the concept of instinct and the analysis of innateness that followed, the constraints that instinct places on learning, and recent work on the genes and neural circuits of innate behavior. The central question is what calling a behavior instinctive explains: classical ethology treated instincts as hardwired circuits that process particular sensory inputs to trigger stereotyped motor outputs, while allowing that internal state and past experience influence them, and one later analysis treats innateness as a set of possibly related natural kinds.

Keywords: instinct, innate behavior, fixed action pattern, ethology, preparedness

Classical works from Tinbergen and Lorenz concluded that instinctive behaviors, including aggression, are mediated by hardwired brain circuitries that specialize in processing certain sensory inputs to trigger stereotyped motor outputs, and further suggested that instinctive behaviors are influenced by an animal's internal state and past experiences (Lischinsky & Lin, 2020). Tinbergen set out the ethological study of instinct in a 1951 monograph (Tinbergen, 1951).

What Instinct Is

MeSH defines instinct as stereotyped patterns of response, characteristic of a given species, that have been phylogenetically adapted to a specific type of situation, and lists Innate Behavior and Fixed Action Pattern among its entry terms. MeSH files the descriptor under motivation and lists no narrower descriptors beneath it.

The concept belongs to ethology as much as to psychology. Tinbergen set out the aims and methods of ethology in a 1963 article (Tinbergen, 1963). He classified four major problems of biology in a 1963 article, and that classification remains valuable in highlighting the value of a comprehensive, multifaceted understanding of a characteristic, with answers to each question providing complementary insights (Bateson & Laland, 2013). The same appraisal adds that new data call for a more nuanced application of Tinbergen's framework (Bateson & Laland, 2013).

Releasers and Fixed Action Patterns

Lorenz's account turned on the releaser. The editor's introduction to his English summary describes the doctrine of releasers as devices for the production of stimuli which serve as the keys to unlock or release innate perceptory patterns, characteristic of the species and the individual, which result in instinctive reactions (Lorenz, 1937). Lorenz and Tinbergen analyzed taxis and the instinctive act in the egg-rolling movement of the greylag goose (Lorenz & Tinbergen, 1939).

The herring gull chick became the classic test case. Hungry herring gull chicks peck at the tip of the parent's bill, a reaction the authors described as innate, and model experiments showed that it is the bill that supplies the key stimuli, while the head is wholly irrelevant in shape, colour and size (Tinbergen & Perdeck, 1951). The bill stimulated pecking through seven properties: its movement, an elongated, not too short and thin shape, lowness, nearness, a downward-pointing posture, a bill spot acting through its red colour and its contrast with the bill, and food protruding from its outline (Table 1; Tinbergen & Perdeck, 1951). By exaggerating some of the bill's relative properties it was possible to construct a supernormal model (Tinbergen & Perdeck, 1951). The case was later reopened as a question of development: Hailman's monograph on the ontogeny of an instinct examined how the pecking response develops in chicks of the laughing gull and related species (Hailman, 1967).

The authors judged that of these properties only the bill spot was a true releaser, in the sense that it does not merely supply key stimuli for the innate begging schema but must be regarded as an adaptation to this signalling function (Tinbergen & Perdeck, 1951).

The movement such a stimulus releases was called a fixed action pattern, and its fixity was itself questioned: Schleidt asked how fixed the fixed action pattern is (Schleidt, 1974), and a later chapter recast such movements as modal action patterns (Barlow, 1977).

The Critique of Instinct

Psychology had its own instinct tradition: the concept was central to McDougall's introduction to social psychology (McDougall, 1908). Within psychology that tradition was soon attacked: Kuo argued for giving up instincts in psychology altogether (Kuo, 1921). The ethological account drew sustained criticism. Peculiar to Lorenz's view was a strong innate-learned dichotomy: he claimed that there are neither ontogenetic nor phylogenetic transitions between instinctive and experience-based behavior components, a position a historical study calls controversial and contrary to all former accounts of instinct (Brigandt, 2005). Lehrman published a critique of Konrad Lorenz's theory of instinctive behavior (Lehrman, 1953), and Beach traced the descent of instinct as a concept in psychology (Beach, 1955). Lorenz had set out the comparative method he applied to innate behaviour patterns (Lorenz, 1950), and the motivational side of such ethological accounts was examined in Hinde's analysis of energy models of motivation (Hinde, 1960). The exchange continued in Lorenz's monograph on the evolution and modification of behavior (Lorenz, 1965) and in Lehrman's later essay on semantic and conceptual issues in the nature-nurture problem (Lehrman, 1970).

The modern form of the debate concerns innateness. Innateness is often defined by appealing to the role of genes in development, to the role of Darwinian evolution, to the non-involvement of learning, to developmental robustness and to modularity, and one analysis argues that all such definitions are unsatisfactory and proposes examining whether the properties associated with the innate and the acquired form theoretically useful clusters, a path it says leads to the view favored by Gilbert Gottlieb that development involves the continuous interplay of the organism and its genes with its environment (Bateson & Mameli, 2007). In Gottlieb's own statement, probabilistic epigenesis is a metatheoretical model of development that emphasizes the reciprocity of influences within and between levels of an organism's developmental manifold and the ubiquity of gene-environment interaction in the realization of all phenotypes (Gottlieb, 2007). The same analysis states the developmental objection directly: in as much as the acquired has been seen in opposition to the innate, the category has been an obstacle to a thorough investigation of how behavior develops (Bateson & Mameli, 2007). A later evaluation argued that simple ways of classifying traits, such as genetically specified versus owing to the environment, are inadequate, and that innateness refers not to a single natural kind but to a set of possibly related natural kinds, including whether a trait is canalized, whether it has a history of natural selection and whether it developed without learning (Mameli & Bateson, 2011). In that analysis, environmental canalization refers to buffering or insensitivity in relation to variations in the environmental conditions met during development, and genetic canalization to buffering relative to variations in the genetic context (Mameli & Bateson, 2011). A rival analysis argues that the concept is irretrievably confused: the vernacular innateness concept is part of folkbiology, so attempts to define it more adequately are unlikely to succeed, and new, neutral terms are preferable for the various related notions needed to understand cognitive development (Griffiths, 2002). A test of that proposal with scenarios about the development of birdsong was argued to explain both the intuitive appeal of existing philosophical analyses of innateness and why they are subject to compelling counterexamples (Griffiths et al., 2009).

Instinct and Learning

Instinct reappeared inside learning theory. Attempting to extend a behavioristically oriented approach to the engineering control of animal behavior by operant conditioning techniques, Breland and Breland reported that they had fought a running battle with the seditious notion of instinct (Breland & Breland, 1961).

Associations are constrained too. When an audiovisual stimulus and a gustatory stimulus were paired with electric shock, rats' avoidance transferred to the audiovisual stimulus but not the gustatory one, whereas when both were paired with toxin or x-ray, avoidance transferred to the gustatory stimulus but not the audiovisual one, so that stimuli appear to be selected as cues depending on the nature of the subsequent reinforcer (Garcia & Koelling, 1966). Seligman generalized the point as a continuum of preparedness, holding that organisms are prepared to associate certain events, unprepared for some and contraprepared for others, and that the assumption of equivalent associability in general process learning theory is false (Seligman, 1970). That conclusion did not settle the matter: Domjan examined the implications of biological constraints on conditioning for general process theory (Domjan, 1983), and McNally reviewed the evidence on preparedness and phobias (McNally, 1987). The theory's account of phobias remains contested. A later review proposed an evolved module for fear learning that is preferentially activated in aversive contexts by stimuli that are fear relevant in an evolutionary perspective (Öhman & Mineka, 2001). A systematic review of 32 fear-conditioning experiments in 23 studies with 1,887 participants found increased resistance to extinction of responses conditioned to snake and spider pictures in 10 (31%) of the experiments, whereas 22 (69%) did not support the hypothesis, and concluded that the evidence suggests preparedness theory does not explain the origin of specific phobias (Åhs et al., 2018).

Genes and Circuits

Genetics has reached complex instinctive behaviors. Oldfield mice build complex burrows with long entrance and escape tunnels, in contrast with the small, simple burrows of deer mice, and both species recapitulate their natural burrowing in the laboratory; in crosses, tunnel length segregated as a complex trait affected by at least three independent genetic regions, whereas the presence of an escape tunnel was associated with a single locus (Weber et al., 2013). The difference appears early: oldfield mice excavated burrows as early as 17 days of age, whereas deer mice did not build burrows until 10 days later, cross-fostering did not alter either species' characteristic burrowing, and a P. polionotus allele linked to adult tunnel length was also associated with precocious onset of burrowing in juveniles (Metz et al., 2017).

Figure 1

Burrow Architecture in Two Sister Species of Peromyscus Mice

Figure 1 sketches the two burrow types. Two sister species of Peromyscus mice differ greatly and heritably in parental behavior; quantitative genetics identified 12 genomic regions that affect parental care, 8 with sex-specific effects, and vasopressin was found to inhibit nest building but not other parental behaviors (Bendesky et al., 2017).

Circuits for innate social behavior have been located. Optogenetic, but not electrical, stimulation of neurons in the ventrolateral subdivision of the ventromedial hypothalamus caused male mice to attack females and inanimate objects as well as males, and pharmacogenetic silencing of the region reversibly inhibited inter-male aggression (Lin et al., 2011). Neurons activated during attack were inhibited during mating, suggesting a potential neural substrate for competition between these opponent social behaviors (Lin et al., 2011). In both flies and mice, relatively small groups of neurons can influence both aggression and mating and also play a part in encoding the internal states that promote them (Anderson, 2016).

Mice respond to a visual display that simulates an approaching object either by initiating escape within a second or by freezing for an extended period, and the probability of these defensive behaviors is strongly dependent on the parameters of the visual stimulus (Yilmaz & Meister, 2013). Escaping from imminent danger is an instinctive behavior, and the probability and vigour of escape in mice scale with the saliency of innate threats and are well described by a model that computes the distance between the threat level and an escape threshold; neurons in the medial superior colliculus represent the saliency of the threat, whereas glutamatergic neurons of the dorsal periaqueductal grey encode the choice to escape and control escape vigour (Evans et al., 2018).

Worked Example

The parental-care study gives the arithmetic of a sex-specific instinct. Quantitative genetics identified 12 genomic regions that affect parental care, of which 8 had sex-specific effects (Bendesky et al., 2017). That is 8 / 12 = 0.67, so two thirds of the regions acted differently in males and females, which is why the authors suggest that parental care can evolve independently in the two sexes (Bendesky et al., 2017).

Discussion

Three conclusions follow for psychology. First, the word instinct names a stimulus-response relation that can be dissected: in gull chicks, the bill supplied the key stimuli, and exaggerating its relative properties produced a supernormal model (Tinbergen & Perdeck, 1951).

Second, innate may not be one property. Innateness has been argued to refer to a set of possibly related natural kinds rather than a single one (Mameli & Bateson, 2011), and on Seligman's account learning itself is shaped by what an organism is prepared to associate (Seligman, 1970).

Third, at least one instinctive behavior, escape, is computed, not merely triggered. Escape in mice follows a threshold computation on threat saliency (Evans et al., 2018), and instinctive behaviors are influenced by internal state and past experience (Lischinsky & Lin, 2020).

Current Directions

Four lines of work are active. Flexibility: a review holds that members of a species express social behaviors in a stereotypical and species-specific way without training because of developmentally hardwired neural circuits, yet that these behaviors are flexible, with the readiness to engage in specific social acts varying widely with reproductive state, social experience and many other internal and external factors (Wei et al., 2021). Conserved circuits: a review describes an evolutionarily conserved core aggression circuit composed of four subcortical regions (Lischinsky & Lin, 2020), and whether the similarities between the circuit nodes for aggression and mating in flies and mice are superficial and coincidental or reflect conserved or analogous modules remains open (Anderson, 2016). Computation: the behavioral principles of escape are evolutionarily conserved and rely on elementary computational steps such as classifying sensory stimuli and executing appropriate movements (Branco & Redgrave, 2020). Evolution: variation in an ancient neuropeptide contributes to interspecific differences in parental care (Bendesky et al., 2017).

Common Misconceptions

“Instincts are fixed and unaffected by experience.”

Classical works from Tinbergen and Lorenz have been read as further suggesting that instinctive behaviors are influenced by an animal's internal state and past experiences (Lischinsky & Lin, 2020).

“Any cue can be linked to any consequence.”

Rats associated tastes with illness but not with shock, and audiovisual cues with shock but not with illness (Garcia & Koelling, 1966).

“Innate simply means genetically specified.”

Classifying traits as genetically specified versus owing to the environment has been argued to be inadequate (Mameli & Bateson, 2011).

Glossary

Canalization.

Buffering of a trait's development against variation in the environmental conditions met during development (environmental canalization) or in the genetic context (genetic canalization); one of the properties the term innate has been argued to pick out.

Contrapreparedness.

The end of the preparedness continuum at which an organism is contraprepared to associate certain events.

Core aggression circuit.

An evolutionarily conserved set of four subcortical regions described as underlying aggression.

Dorsal periaqueductal grey.

A midbrain region whose glutamatergic neurons encode the choice to escape and control escape vigour in mice.

Ethology.

The biological study of behavior whose four major problems Tinbergen classified in 1963.

Fixed action pattern.

A stereotyped motor output that, on the classical account, hardwired circuits trigger in response to certain sensory inputs.

Innate behavior.

Behavior classed as innate, a label one analysis takes to cover several distinct properties rather than one.

Key stimulus.

A property of an object, such as the parent gull's bill, that elicits a response classical ethologists described as innate.

Looming stimulus.

A visual display simulating an approaching object, to which mice respond by escape or freezing.

Preparedness.

A continuum on which organisms are prepared to associate certain events, unprepared for some and contraprepared for others.

Releaser.

In Lorenz's account, a device for producing stimuli that release innate perceptory patterns resulting in instinctive reactions.

Superior colliculus.

A midbrain structure whose medial deep-layer neurons represent the saliency of a threat stimulus in mice.

Supernormal stimulus.

A model built by exaggerating relative properties of a natural stimulus, such as a gull's bill.

Vasopressin.

A neuropeptide that inhibited nest building but not other parental behaviors in mice.

Ventromedial hypothalamus.

A hypothalamic nucleus whose ventrolateral neurons, when stimulated optogenetically, caused male mice to attack.

Key Researchers

David J. Anderson

(b. 1956). Neuroscientist at the California Institute of Technology and the Howard Hughes Medical Institute; co-authored the identification of an aggression locus in the mouse hypothalamus. ORCID - Wikipedia - Wikidata - Faculty Page

Patrick Bateson

(1938-2017). Ethologist at the University of Cambridge; co-authored evaluations of the concept of innateness and of Tinbergen's four questions. Wikidata - Wikipedia

Frank A. Beach

(1911-1988). Comparative psychologist at the University of California, Berkeley; wrote on the descent of instinct. Wikipedia

Tiago Branco

Neuroscientist at the Sainsbury Wellcome Centre, University College London; co-authored the synaptic threshold model of escape decisions in mice. Faculty Page

Hopi E. Hoekstra

(b. 1972). Evolutionary biologist at Harvard University; co-authored the genetic studies of burrowing and parental care in Peromyscus mice. ORCID - Wikipedia - Wikidata - Faculty Page

Daniel S. Lehrman

(1919-1972). Comparative psychologist at the Institute of Animal Behavior, Rutgers University; wrote a critique of the ethological theory of instinctive behavior. Wikipedia - Wikidata

Konrad Lorenz

(1903-1989). Ethologist at the Max Planck Institute for Behavioral Physiology; developed the doctrine of releasers. Wikidata - Wikipedia

Nikolaas Tinbergen

(1907-1988). Ethologist at the University of Oxford; studied the stimuli releasing begging in herring gull chicks and classified the four major problems of biology. Wikidata - Wikipedia

Frequently Asked Questions

What is instinct in psychology?

MeSH describes instinct as stereotyped patterns of response, characteristic of a given species, and classical ethology held that instinctive behaviors are mediated by circuits that process certain sensory inputs to trigger stereotyped motor outputs (Lischinsky & Lin, 2020).

What is a fixed action pattern?

It is the stereotyped motor output of the classical account of instinct, and how fixed it really is has been questioned (Schleidt, 1974).

What is a supernormal stimulus?

It is a model that exaggerates relative properties of a natural stimulus; one exaggerated model of a gull's bill worked as a supernormal stimulus for chicks (Tinbergen & Perdeck, 1951).

Who criticized the idea of instinct?

Lehrman wrote a critique of Konrad Lorenz's theory of instinctive behavior (Lehrman, 1953).

Is innate the same as genetic?

Not on one analysis, which argues that innateness refers to a set of possibly related natural kinds rather than a single one (Mameli & Bateson, 2011).

How does instinct affect learning?

On Seligman's account, organisms are prepared to associate certain events and contraprepared for others, so not all events are equally associable (Seligman, 1970). Its account of phobias is contested: a systematic review concluded that the evidence suggests preparedness theory does not explain the origin of specific phobias (Åhs et al., 2018).

Are there brain circuits for instinctive behavior?

Optogenetic stimulation of neurons in the ventrolateral ventromedial hypothalamus caused male mice to attack (Lin et al., 2011).

Is escape from danger instinctive?

Escaping from imminent danger is an instinctive behavior, and in mice its probability and vigour scale with the saliency of innate threats (Evans et al., 2018).

References